Multicomponent Synthesis and Biological Evaluation of a Piperazine-Based Dopamine Receptor Ligand Library

Enantiopure β-isocyano-boronic esters: synthesis and exploitation in isocyanide-based multicomponent reactions

Various boron-containing isocyanides have been efficiently synthesized from the corresponding enantiopure β-substituted β-amino boronic acid pinacol esters, without need for protecting group interconversion, through a two-step, purification-free procedure. They were employed in a variety of isocyanide-based multicomponent reactions, proving to be reliable components for all of them and allowing the efficient synthesis of unprecedented, boron-containing peptidomimetics and heteroatom-rich small molecules, including biologically relevant cyclic boronates. Jointing together the β-amido boronic acid moiety, deriving from the isocyanide component, with prominent pharmacophoric rings emerging from the multicomponent process, a successful application of the molecular hybridization concept could be realized.

Isonitrile-Based Multicomponent Synthesis of β-Amino Boronic Acids as β-Lactamase Inhibitors

The application of various isonitrile-based multicomponent reactions to protected (2-oxoethyl)boronic acid (as the carbonyl component) is described. The Ugi reaction, both in the four components and in the four centers-three components versions, and the van Leusen reaction, proved effective at providing small libraries of MIDA-protected β-aminoboronic acids. The corresponding free β-aminoboronic acids, quantitatively recovered through basic mild deprotection, were found to be quite stable and were fully characterized, including by 11B-NMR spectroscopy. Single-crystal X-ray diffraction analysis, applied both to a MIDA-protected and a free β-aminoboronic acid derivative, provided evidence for different conformations in the solid-state. Finally, the antimicrobial activities of selected compounds were evaluated by measuring their minimal inhibitory concentration (MIC) values, and the binding mode of the most promising derivative on OXA-23 class D β-lactamase was predicted by a molecular modeling study.

Synthesis, Molecular Properties Estimations, and Dual Dopamine D2 and D3 Receptor Activities of Benzothiazole-Based Ligands

Neurleptic drugs, e.g., aripiprazole, targeting the dopamine D_2S and D₃ receptors (D_2SR and D₃R) in the central nervous system are widely used in the treatment of several psychotic and neurodegenerative diseases. Therefore, a new series of benzothiazole-based ligands (3-20) was synthesized by applying the bioisosteric approach derived from the selective D₃Rs ligand BP-897 (1) and its structurally related benz[d]imidazole derivative (2). Herein, introduction of the benzothiazole moiety was well tolerated by D_2SR and D₃R binding sites leading to antagonist affinities in the low nanomolar concentration range at both receptor subtypes. However, all novel compounds showed lower antagonist affinity to D₃R when compared to that of 1. Further exploration of different substitution patterns at the benzothiazole heterocycle and the basic 4-phenylpiperazine resulted in the discovery of high dually acting D_2SR and D₃R ligands. Moreover, the methoxy substitution at 2-position of 4-phenylpiperazine resulted in significantly (22-fold) increased D_2SR binding affinity as compared to the parent ligand 1, and improved physicochemical and drug-likeness properties of ligands 3-11. However, the latter structural modifications failed to improve the drug-able properties in ligands having un-substituted 4-phenylpiperazine analogs (12-20). Accordingly, compound 9 showed in addition to high dual affinity at the D_2SR and D₃R [K_i (hD_2SR) = 2.8 ± 0.8 nM; K_i (hD₃R) = 3.0 ± 1.6 nM], promising clogS, clogP, LE (hD_2SR, hD₃R), LipE (hD_2SR, hD₃R), and drug-likeness score values of −4.7, 4.2, (0.4, 0.4), (4.4, 4.3), and 0.7, respectively. Also, the deaminated analog 10 [K_i (hD_2SR) = 3.2 ± 0.4 nM; K_i (hD₃R) = 8.5 ± 2.2 nM] revealed clogS, clogP, LE (hD_2SR, hD₃R), LipE (hD_2SR, hD₃R) and drug-likeness score values of −4.7, 4.2, (0.4, 0.4), (3.9, 3.5), and 0.4, respectively. The results observed for the newly developed benzothiazole-based ligands 3-20 provide clues for the diversity in structure activity relationships (SARs) at the D_2SR and D₃R subtypes.

One-Pot Multicomponent Synthesis of Glycopolymers through a Combination of Host-Guest Interaction, Thiol-ene, and Copper-Catalyzed Click Reaction in Water

There is a common phenomenon that the heterogeneity of natural oligosaccharides contains various sugar units, which can be used to enhance affinity and selectivity toward a specific receptor, so the synthesis of heterogeneous glycopolymers is always an important issue in the glycopolymer field. Herein, this study conducts a one-pot method to prepare polyrotaxane-based heteroglycopolymers anchored with different sugar units and fluorescent moieties via the combination of host-guest interaction, thiol-ene, and copper-catalyzed click chemistry in water. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, X-ray diffraction, and Ellman's assay test are used in the paper to characterize the compounds. Quartz crystal microbalance-dissipation (QCD-D) experiments and bacterial adhesion assay are utilized to study the interactions of polyrotaxane-based heteroglycopolymers with Con A and Escherichia coli. The results reveal that polyrotaxanes (PRs) with mannose and glucose present better specificity toward Con A and E. coli than PRs with glucose due to synergistic effects.

Novel Bivalent Ligands Based on the Sumanirole Pharmacophore Reveal Dopamine D2 Receptor (D2R) Biased Agonism

The development of bivalent ligands has attracted interest as a way to potentially improve the selectivity and/or affinity for a specific receptor subtype. The ability to bind two distinct receptor binding sites simultaneously can allow the selective activation of specific G-protein dependent or β-arrestin-mediated cascade pathways. Herein, we developed an extended SAR study using sumanirole (1) as the primary pharmacophore. We found that substitutions in the N-1- and/or N-5-positions, physiochemical properties of those substituents, and secondary aromatic pharmacophores can enhance agonist efficacy for the cAMP inhibition mediated by G_i/o-proteins, while reducing or suppressing potency and efficacy toward β-arrestin recruitment. Compound 19 was identified as a new lead for its selective D₂ G-protein biased agonism with an EC₅₀ in the subnanomolar range. Structure-activity correlations were observed between substitutions in positions N-1 and/or N-5 of 1 and the capacity of the new bivalent compounds to selectively activate G-proteins versus β-arrestin recruitment in D₂R-BRET functional assays.

Diversity oriented synthesis of β-carbolinone and indolo-pyrazinone analogues based on an Ugi four component reaction and subsequent cyclisation of the resulting indole intermediate

One pot two step synthesis of β-carbolinone and indolo-pyrazinone analogues via acid mediated cyclisation of Ugi intermediate has been developed with a wide substrate scope.